Microplastics in Tea: Unveiling a Hidden Health Risk

Authored By: Kersten Sykes

Art By: Julia Chen

Second only to water, tea has rightfully earned its place as one of the most popular beverages on the planet. Tea serves as a fundamental drink in a myriad of cultural traditions. Whether it is a cup of black, green, oolong or herbal, tea is considered a low calorie option. Additionally, tea is known to contain health-promoting phytochemicals such as theaflavins, thearubigns, flavonols, cathechins which serve as antioxidants that can combat inflammation [1]. One recent concern for frequent tea drinkers is the implementation of plastic tea bags. For consumers, this poses a sizeable concern: the potential contamination by microplastics (MPs) which are expelled during the brewing process.

Plastic and its subsequent MPs are encountered daily and are commonly used in disposable packaging for food and beverages. Although ingestion is the primary path of entry for plastic, inhalation and direct dermal contact are also possible [2]. Even when plastic is not “seemingly present” there is still a possibility for ingesting microplastics as seen with the trophic transfer of MPs within seafood [3]. Interestingly research has found that globally 81% of tap water contains microplastics [4]. Luckily the MPs are present in relatively low amounts with a mean concentration of 5.45 particles per liter. Moreover, it is not just the plastic material like polyethylene and nylon that pose a possible worry but the chemical additives such as phthalates that are combined with plastic polymers within the final material product [2]. So why are plastic tea bags causing such a stir? One possible reason is the tea bag’s exposure to high temperatures within a fluid medium (like hot water). This allows any possible MPs and chemicals to become suspended in the tea and be easily ingested.

One primary study by scientists (Kashfi et al. 2023) investigated the extent in which microplastics and subsequent chemicals are present from plastic tea bags [5]. The study used 45 different plastic tea bag samples across 15 respective brands. The procedure involved emptying the internal contents and rinsing the tea bag before submerging it within 250 mL of 95 degrees Celsius deionized water; they allowed it to steep for five minutes before leaving it at room temperature for an additional 3 hours. The sample solution was filtered and any chemical additives were separated from plastic material in order to analyze each respectively. It was found that, on average, a sample contained approximately 150 to 400 MP particles ranging in size from 100 to 250 micrometers. It was identified that the primary types of plastic present were 53.9% polyethylene, 42.3% nylon and 3.8% polycarbonate. Additionally, for the presence of chemical additives such as phthalate esters (PAEs) 2.37mg to 2.87mg were found per gram of sample liquid. The primary types of phthalates found were diethylhexyl phthalates and diisobutyl phthalates. From the study’s results, it was concluded that relatively high amounts of MPs and PAEs are released by plastic mesh tea bags. This posed a significant health risk for consumers.

Although MP consumption is generally known by the public to pose health risks, there are key biological mechanisms causing these effects. Increased immunoglobulin A levels can result in excess oxidative stress (i.e. inflammation) which is associated with cancer development. A recent study found that long-term consumption of polyethylene microplastics by mice led to elevated levels of the antibody immunoglobulin A and increased levels of neutrophils, a type of white blood cell [6]. The majority of microplastic accumulation was found to centralize within the stomach lining and spleen cells resulting in damaged organelles. Moreover, as found in another study of mice, exposure to polyethylene microplastics was found to decrease regulatory T cell counts and increase the proportion of Th17 cells which both lead to excessive inflammation within the body [7].

Based on the current research available, any health-conscious consumer should avoid using any form of plastic mesh tea bags. Luckily, other brewing methods such as loose-leaf and fiber-based tea bags serve as easily accessible alternatives. It is imperative that media and academic publications alike differentiate between the benefits that come from the contents of the tea itself and the precautions surrounding the use of plastic tea bags.

References:

1. Khan, N., & Mukhtar, H. (2013). Tea and Health: Studies in Humans. Current Pharmaceutical Design, 19(34), 6141–6147.

2. Goodes, L. M., Wong, E. V. S., Alex, J., Mofflin, L., Toshniwal, P., Brunner, M., Solomons, T., White, E., Choudhury, O., Seewoo, B. J., Mulders, Y. R., Dale, T., Newman, H. J., Naveed, A., Lowe, A. B., Hendrie, D. V., Symeonides, C., & Dunlop, S. A. (2022). A scoping review protocol on in vivo human plastic exposure and health impacts. Systematic Reviews, 11(1), 137. https://doi.org/10.1186/s13643-022-02010-6

3. Carbery, M., O’Connor, W., & Palanisami, T. (2018). Trophic transfer of microplastics and mixed contaminants in the marine food web and implications for human health. Environment International, 115, 400–409. https://doi.org/10.1016/j.envint.2018.03.007

4. Kosuth, M., Mason, S. A., & Wattenberg, E. V. (2018). Anthropogenic contamination of tap water, beer, and sea salt. PLOS ONE, 13(4), e0194970. https://doi.org/10.1371/journal.pone.0194970

5. Kashfi, F. S., Mohammadi, A., Rostami, F., Savari, A., De-la-Torre, G. E., Spitz, J., Saeedi, R., Kalantarhormozi, M., Farhadi, A., & Dobaradaran, S. (2023). Microplastics and phthalate esters release from teabags into tea drink: Occurrence, human exposure, and health risks. Environmental Science and Pollution Research, 30(47), 104209–104222. https://doi.org/10.1007/s11356-023-29726-9

6. Park, E.-J., Han, J.-S., Park, E.-J., Seong, E., Lee, G.-H., Kim, D.-W., Son, H.-Y., Han, H.-Y., & Lee, B.-S. (2020). Repeated-oral dose toxicity of polyethylene microplastics and the possible implications on reproduction and development of the next generation. Toxicology Letters, 324, 75–85. https://doi.org/10.1016/j.toxlet.2020.01.008

7. Hirt, N., & Body-Malapel, M. (2020). Immunotoxicity and intestinal effects of nano- and microplastics: A review of the literature. Particle and Fibre Toxicology, 17(1), 57. https://doi.org/10.1186/s12989-020-00387-7